v^2-u^2=2 x a x d
25^2-0^2=2 x a x 70
625-0=140 x a
625=140a
a=625/140
a=4.46 m/s^2
im not very sure but i think this is how you do this
Answer:
The diameter of the needle is <u>4.675 cm</u>.
Explanation:
Given:
Volume flow rate is, 
Velocity of air expelled by pump is, 
Let the area of the needle be 'A' cm² and the diameter be 'd' cm.
We know that, volume flow rate of the air expelled by pump is given as the product of the needle's area and velocity of air flowing through that area.
Therefore, volume flow rate is given as:

Now, considering the needle to be circular, area of the needle can be written as:

Therefore, the diameter of the needle is 4.675 cm.
Answer:
is there any choice? in this question?
In his celebrated Second Law of Motion, Newton wrote:
Net force = (mass) x (acceleration).
By the process of "plugging in numbers", we can write
1255 N = (41 kg) x (acceleration)
Now, after dividing each side by (41 kg), we have
(1255 N) / (41 kg) = acceleration.
But (1255N)/(41kg) = 30.61 m/s² .
So unless we have carelessly blooped the calculations somewhere,
that 30.61 m/s² is the answer we're looking for.